An attractive hairstyle is nowadays generally regarded as an indispensable part of a well-groomed appearance. In order to achieve such an attractive hairstyle, the hair is subjected to cosmetic treatment methods ranging from cleaning by means of a shampoo to permanent shaping by means of chemical/thermal processes or permanent oxidative color lightening. For coloring the hair, substantive dyes and oxidation dyes of limited shelf life are available. These hair dyes are usually applied to the hair in the form of liquid or foam-type preparations. Brushes or foam dispensers are used as aids when applying the dye preparations.
Foam dispensers include, in particular, pump sprays or aerosol sprays, by means of which the cosmetic preparations are sprayed via a valve either by means of mechanical force or with the aid of a propellant. Both methods have obvious disadvantages. While pump sprays are generally not suitable for a sustained and even spray application of cosmetic hair preparations, aerosol sprays are based on the use of propellants or propellant gases, which on the one hand have no cosmetic effect and on the other hand can pose a risk to consumers if not handled correctly.
Against this background, there is a need for alternative ways of atomizing or foaming cosmetic hair preparations. Flash evaporation has proven to be advantageous as one such alternative spraying method. In this method, which is described for example in international patent application WO 200183071 A1 (Henkel), a liquid or paste-like solvent-containing composition is heated in a closed chamber to a temperature above the boiling point of the solvent, thereby generating an overpressure in the composition. When the pressure is released (throttled), the liquid evaporates and can then be atomized for example by means of a suitable nozzle.
Therefore, although flash evaporation is suitable in principle for the spray application of cosmetic hair preparations, at the same time it is not possible to atomize every cosmetic hair preparation by means of a flash evaporation method. This is due on the one hand to the heating of the cosmetic preparation that is necessary for the flash evaporation, and on the other hand to the specifics of the spray mist produced by flash evaporation, for example the droplet size and droplet density produced in the spray mist.
It is therefore desirable to provide specific cosmetic hair preparations for coloring keratin fibers, which on account of their chemical and physical properties are suitable for targeted spray application by means of a device for flash evaporation. The preparations should be suitable for achieving a good cosmetic effect after application by means of a flash evaporation method. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.